The aim of this study is to explore what happened -- and why -- in a collaboration between ourselves as researchers and school leaders from two different schools in Sweden. The theory of practice architectures is used to frame the study. The goal of the collaboration was to enhance the scientific foundation of school practices, which motivated the use of action research as the methodological approach for designing the collaboration. The results allow us to propose a number of critical aspects to take into consideration when establishing a collaboration between researchers and school leaders. The first aspect concerns aiming for "co-ownership" and an "equivalent collaboration." These involve trustful and respectful relations, empowering individuals in their professional roles. The second aspect is linked to attention to "local infrastructures" and the importance of organisational settings that facilitate a holistic approach and a shared understanding of the aims of both the research and the collaboration. The third and final aspect is related to "school leaders' legitimacy to organise research-based school improvements." School leaders are responsible for educational quality in schools, and this makes them best suited for leading school improvements. However, theoretical frameworks and methods introduced by researchers can support the ambition to enhance the scientific foundation of school practices. We advocate the development of practices inhabited by school practitioners and school researchers within the "educational complex." In addition, we promote the creation of healthy environments in the form of arrangements that create spaces where equivalent collaborations, shared responsibility and co-ownership may grow.